From b2f8930e558a0de69d2c9fbc4def64bc81c1e1af Mon Sep 17 00:00:00 2001
From: Thorsrud22 <229304553+Thorsrud22@users.noreply.github.com>
Date: Sun, 13 Sep 2026 20:56:31 +0200
Subject: [PATCH] fix: raise a clear TypeError when convert() is given a
 non-str

Passing a list of lines to Ansi2HTMLConverter.convert() (or prepare())
used to fail deep inside the regex pass with
"AttributeError: 'list' object has no attribute 'replace'", which
gives no hint about what was wrong or how to fix it. Two users reported
hitting this (#242).

Check the input type once at the entry point and raise a TypeError
that names the actual type and suggests joining the lines first.

Fixes #242
---
 src/ansi2html/converter.py | 6 ++++++
 tests/test_ansi2html.py    | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/ansi2html/converter.py b/src/ansi2html/converter.py
index c9f29fd..774c820 100644
--- a/src/ansi2html/converter.py
+++ b/src/ansi2html/converter.py
@@ -607,6 +607,12 @@ def prepare(
     ) -> Attributes:
         """Load the contents of 'ansi' into this object"""
 
+        if not isinstance(ansi, str):
+            raise TypeError(
+                "ansi must be a str, not %s; join an iterable of lines first, "
+                "e.g. ''.join(lines)" % type(ansi).__name__
+            )
+
         body, styles = self.apply_regex(ansi)
 
         if ensure_trailing_newline and _needs_extra_newline(body):
diff --git a/tests/test_ansi2html.py b/tests/test_ansi2html.py
index fedb954..e9e0d8b 100644
--- a/tests/test_ansi2html.py
+++ b/tests/test_ansi2html.py
@@ -29,6 +29,8 @@
 from typing import List
 from unittest.mock import patch
 
+import pytest
+
 from ansi2html import Ansi2HTMLConverter
 from ansi2html.converter import (
     ANSI_BLINK_FAST,
@@ -57,6 +59,12 @@ def test_linkify(self) -> None:
         html = Ansi2HTMLConverter(linkify=True).convert(ansi)
         assert target in html
 
+    def test_convert_rejects_non_str_input(self) -> None:
+        # Passing a list of lines used to surface as an unhelpful
+        # AttributeError deep inside apply_regex (see #242).
+        with pytest.raises(TypeError, match="must be a str, not list"):
+            Ansi2HTMLConverter().convert(["a", "b"])  # type: ignore[arg-type]
+
     def test_not_linkify(self) -> None:
         ansi = "http://threebean.org"
         target = '<a href="http://threebean.org">http://threebean.org</a>'